assertEquals(v2, v1, "expected " + v2 + " == " + v1);
            assertEquals(v1.hashCode(), v2.hashCode(), "expected #(" + v1 + ") == #(" + v1 + ")");
        }
    }

    protected void assertSequence(String... versions) {
        for (int i = 0; i < versions.length - 1; i++) {
            for (int j = i + 1; j < versions.length; j++) {
                assertOrder(X_LT_Y, versions[i], versions[j]);
            }